package net.minecraft.client.renderer.chunk;

import it.unimi.dsi.fastutil.longs.Long2ObjectFunction;
import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
import net.fabricmc.api.EnvType;
import net.fabricmc.api.Environment;
import net.minecraft.client.multiplayer.ClientLevel;
import net.minecraft.core.SectionPos;
import net.minecraft.world.level.Level;
import net.minecraft.world.level.chunk.LevelChunk;

@Environment(EnvType.CLIENT)
public class RenderRegionCache {
	private final Long2ObjectMap<SectionCopy> sectionCopyCache = new Long2ObjectOpenHashMap<>();

	public RenderSectionRegion createRegion(final ClientLevel level, final long sectionNode) {
		int sectionX = SectionPos.x(sectionNode);
		int sectionY = SectionPos.y(sectionNode);
		int sectionZ = SectionPos.z(sectionNode);
		int minSectionX = sectionX - 1;
		int minSectionY = sectionY - 1;
		int minSectionZ = sectionZ - 1;
		int maxSectionX = sectionX + 1;
		int maxSectionY = sectionY + 1;
		int maxSectionZ = sectionZ + 1;
		SectionCopy[] regionSections = new SectionCopy[27];

		for (int regionSectionZ = minSectionZ; regionSectionZ <= maxSectionZ; regionSectionZ++) {
			for (int regionSectionY = minSectionY; regionSectionY <= maxSectionY; regionSectionY++) {
				for (int regionSectionX = minSectionX; regionSectionX <= maxSectionX; regionSectionX++) {
					int index = RenderSectionRegion.index(minSectionX, minSectionY, minSectionZ, regionSectionX, regionSectionY, regionSectionZ);
					regionSections[index] = this.getSectionDataCopy(level, regionSectionX, regionSectionY, regionSectionZ);
				}
			}
		}

		return new RenderSectionRegion(level, minSectionX, minSectionY, minSectionZ, regionSections);
	}

	private SectionCopy getSectionDataCopy(final Level level, final int sectionX, final int sectionY, final int sectionZ) {
		return this.sectionCopyCache.computeIfAbsent(SectionPos.asLong(sectionX, sectionY, sectionZ), (Long2ObjectFunction<? extends SectionCopy>)(k -> {
			LevelChunk chunk = level.getChunk(sectionX, sectionZ);
			return new SectionCopy(chunk, chunk.getSectionIndexFromSectionY(sectionY));
		}));
	}
}